From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) by kanga.kvack.org (Postfix) with ESMTP id 021BA8E0018 for ; Mon, 10 Dec 2018 11:04:09 -0500 (EST) Received: by mail-wr1-f69.google.com with SMTP id d6so588061wrm.19 for ; Mon, 10 Dec 2018 08:04:08 -0800 (PST) Received: from EUR03-AM5-obe.outbound.protection.outlook.com (mail-eopbgr30040.outbound.protection.outlook.com. [40.107.3.40]) by mx.google.com with ESMTPS id q16si8475053wme.90.2018.12.10.08.04.05 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 10 Dec 2018 08:04:05 -0800 (PST) From: Steve Capper Subject: Re: [PATCH V5 5/7] arm64: mm: Prevent mismatched 52-bit VA support Date: Mon, 10 Dec 2018 16:04:02 +0000 Message-ID: <20181210160348.GA4564@capper-debian.cambridge.arm.com> References: <20181206225042.11548-1-steve.capper@arm.com> <20181206225042.11548-6-steve.capper@arm.com> <81860712-ff5f-5a51-d39e-9db9e3d31a26@arm.com> <20181207152529.GB2682@edgewater-inn.cambridge.arm.com> <20181210133640.GA31425@edgewater-inn.cambridge.arm.com> In-Reply-To: <20181210133640.GA31425@edgewater-inn.cambridge.arm.com> Content-Language: en-US Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Will Deacon Cc: Suzuki Poulose , "linux-mm@kvack.org" , "linux-arm-kernel@lists.infradead.org" , Catalin Marinas , "ard.biesheuvel@linaro.org" , "jcm@redhat.com" , nd On Mon, Dec 10, 2018 at 01:36:40PM +0000, Will Deacon wrote: > On Fri, Dec 07, 2018 at 05:28:58PM +0000, Suzuki K Poulose wrote: > >=20 > >=20 > > On 07/12/2018 15:26, Will Deacon wrote: > > > On Fri, Dec 07, 2018 at 10:47:57AM +0000, Suzuki K Poulose wrote: > > > > On 12/06/2018 10:50 PM, Steve Capper wrote: > > > > > diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S > > > > > index f60081be9a1b..58fcc1edd852 100644 > > > > > --- a/arch/arm64/kernel/head.S > > > > > +++ b/arch/arm64/kernel/head.S > > > > > @@ -707,6 +707,7 @@ secondary_startup: > > > > > /* > > > > > * Common entry point for secondary CPUs. > > > > > */ > > > > > + bl __cpu_secondary_check52bitva > > > > > bl __cpu_setup // initialise processor > > > > > adrp x1, swapper_pg_dir > > > > > bl __enable_mmu > > > > > @@ -785,6 +786,31 @@ ENTRY(__enable_mmu) > > > > > ret > > > > > ENDPROC(__enable_mmu) > > > > > +ENTRY(__cpu_secondary_check52bitva) > > > > > +#ifdef CONFIG_ARM64_52BIT_VA > > > > > + ldr_l x0, vabits_user > > > > > + cmp x0, #52 > > > > > + b.ne 2f > + > > > > > + mrs_s x0, SYS_ID_AA64MMFR2_EL1 > > > > > + and x0, x0, #(0xf << ID_AA64MMFR2_LVA_SHIFT) > > > > > + cbnz x0, 2f > > > > > + > > > > > + adr_l x0, va52mismatch > > > > > + mov w1, #1 > > > > > + strb w1, [x0] > > > > > + dmb sy > > > > > + dc ivac, x0 // Invalidate potentially stale cache line > > > >=20 > > > > You may have to clear this variable before a CPU is brought up to a= void > > > > raising a false error message when another secondary CPU doesn't bo= ot > > > > for some other reason (say granule support) after a CPU failed with= lack > > > > of 52bitva. It is really a crazy corner case. > > >=20 > > > Can't we just follow the example set by the EL2 setup in the way that= is > > > uses __boot_cpu_mode? In that case, we only need one variable and you= can > > > detect a problem by comparing the two halves. > >=20 > > The only difference here is, the support is bolted at boot CPU time and= hence > > we need to verify each and every CPU, unlike the __boot_cpu_mode where = we > > check for mismatch after the SMP CPUs are brought up. If we decide to m= ake > > the choice later, something like that could work. The only caveat is th= e 52bit > > kernel VA will have to do something like the above. >=20 > So looking at this a bit more, I think we're better off repurposing the > upper bits of the early boot status word to contain a reason code, rather > than introducing new variables for every possible mismatch. >=20 > Does the untested diff below look remotely sane to you? >=20 > Will >=20 Thanks Will, This looks good to me, I will test now and fold this into a patch. Cheers, --=20 Steve